Apparatus for severing well casing in a submarine environment



sept. 23, 1969 S. H. SMITH APPARATUS FOR SEVERING WELL CASING IN ASUBMARINE ENVIRONMENT Drgnal Filed Sept. 9. 1966 2 Sheets-Sheet 1 Sept.23, 1969 s. H. sM'lTH 3,468,373

APPARATUS FOR SEVERING WELL CASINGIN A SUBMARINE ENVIRONMENT OriginalFiled Sept. 9, 1966 2 Sheets-Sheet 2 l E74 f=' i INVENTOR.

SAMUEL H. 544/777' TTOP/VE-YS United States Patent O 3,468,373 APPARATUSFOR SEVERING WELL CASING IN A SUBMARINE ENVIRONMENT Samuel H. Smith,2224 NW. 52nd St., Oklahoma City, Okla. 73112 Original application Sept.9, 1966, Ser. No. 573,326, now Patent No. 3,378,072, dated Apr. 16,1968. Divided and this application Jan. 2, 1968, Ser. No. 705,589

Int. Cl. E21h 29/00, 43/112 U.S. Cl. 166-55.8 3 Claims ABSTRACT OF THEDISCLOSURE Apparatus for cutting submerged multi-tubular well casingwhich includes an elongated tubing string dimensioned for passage intothe innermost casing string and carrying a rotary casing cutting toolsimilarly dimensioned. The tool includes a plurality of elongatedcutting members detachably and pivotally secured to the body of the toolfor pivotation about a horizontal axis into cutting engagement with theinnermost casing string, and shorter than required to Contact theinternal wall of the outermost casing string. A piston mechanism isprovided in the cutting tool for pivoting the cutting members intocutting position7 and a plurality of longer cutting members are providedfor interchanging with those pivotally secured to the body ot' thecutting tool for the purpose of cutting through one or more casingstrings located outwardly of the innermost casing string after thelatter casing string has been severed. A plurality of variable lengthconnecting subs are provided for insertion in the elongated tubingstring in order to adjust the position of the cutting tool in theinnermost casing string.

Related applications This application is a division of co-pending UnitedStates application Ser. No. 578,326 led Sept. 9, 1966, entitled Methodand Apparatus for Severing Well Casing in a Submarine Environment, whichapplication has now issued as United States Patent 3,378,072.

This invention relates to oit-shore or submarine hydrocarbon explorationand production techniques, and more specifically, but not by way oflimitation, relates to an apparatus which can be employed for cutting orsevering a well casing extended into the oor of the ocean or sea for thepurpose of recovering hydrocarbons.

With the relatively recent advent of exploration and production ofpetroleum from subterranean deposits located beneath the oecans andseas, radical modifications in conventional drilling and productiontechniques used in onshore exploration and production have beendemanded. Many problems which are not experienced in traditionaldrilling and production have been encountered in the case of offshoreoperations.

One of the difculties which has been experienced in olshore drilling andproduction is the problem of providing a sufficiently stable platform orSupporting structure on which the drilling equipment may be mounted, andfrom which the drill string or production tubing can be extended andmade to function eliectively. In relatively deep waters where the use ofa supporting structure rested upon the bottom of a body of water becomesimpractical, drilling has been attempted and carried out with somesuccess from oating platforms. In this case, however, difficulties andrelatively greater expense continue to result from the necessity toaccommodate the drilling equipment and steps employed to wave and swellaction which continually change the position of the drilling barge orother point of origin of the drill string with respect to the locationon the bottom of the ocean or sea where the 3,468,373 Patented Sept. 23,1969 ICC actual bore hole is to be formed. Telescoping slip joints andsimilar structures have been provided in drill strings to permit acertain amount of play and variation in length of the string to randomlyoccur as may be required as a result from the necessity to accommodatethed rilling platform. There has also been recently developed, a swivelstructure which is incorporated in the drill string and which cooperateswith or rests upon the borehole casing to limit the movement of thatportion of the drill string which is positioned within the casing, andthus make easier to carry out certain operations which must be carriedout down hole by reason of improved stability in the location ofthedownhole tools.

An operation which frequently must be conducted following a drillingoperation which, for one reason or another has been terminated and nofurther utilization of the well head equipment contemplated, is theseverance or cutting of the borehole casing at some point below the wellhead so that the upper portion of the casing and the valuable weil headequipment attached thereto can be recovered from the ocean oor andreutilized in other drilling and production operations. The difficultyof successfully and economically accomplishing such cutting andseverance of the well casing has been considerably augmented in the caseof oishore wells by the fact that it is the usual and conventionalpractice in such wells to provide a plurality of concentric casingstrings, all of which must be cut through in order to permit the wellhead equipment which is attached to the top of these casing strings tobe extracted or recovered from the ocean loor. The equipment which hasbeen most widely employed for the purpose of cutting the casing a shortdistance below the well head has been a cutter tool usually including aplurality of cutter knives which are pivotally attached to the body ofthe cutting tool and can be extended radially outwardly therefrom intocontact with the casing preparatory to the cutting operation. The tubingstring which carries the cutting tool is then rotated within the casingso that the knives bear against the casing as they are rotated andeventually cut or abrade through the casing and permit the severed upperportion thereof to be removed.

While, in a few instances, cutting tools of this type have beensatisfactory for the severance of the well casing, great diiculty hasbeen experienced in reliably and quickly cutting through those casingstructures most widely used in offshore drilling which include aplurality of concentric tubular casing members which must all be cutbefore the well head equipment can be freely moved. With the cuttingtools and techniques previously in use, severing this multiple casingstructure has been a. time consuming and expensive operation, and it hasbeen extremely diicult on many occasions to know with certainty whetherthe cutting tool has completely severed the several concentric casingstructures, with the result that frequently the operation is carried onmuch longer than necessary in order to be relatively assured of thisfact.

The diiculty which has been experienced in the severance of the severalconcentric casing strings with the cutting tools previously in use hasbeen largely due to the limited space which is available Within theinnermost casing string, and the inability, because of such spacelimitations, to obtain adequate leverage and cutting efciency withcutting knives sufficiently large to extend completely through theoutermost of the casing strings in the `tinal phases of the cuttingoperation.

The present invention involves an improved apparatus for accomplishingthis severance or cutting of a submarine well casing of the type inwhich several tubular casing members are telescopingly disposedrelatively to each other. The apparatus which is employed in permitssuch multiple concentric casing strings to be cut through in a muchshorter time than prior techniques in use have permitted, and furthergives a much greater assurance at the surface control point of theeffectiveness and the success of the cutting operation, and of itsprogress over each interval of time.

The well casing severing apparatus of the invention includes a cuttingtool of the type having pivotally secured thereto at least one elongatedcutting member. The point at which the cutting tool is positioned withinthe innermost casing string will be selected according to currentconventional practices, and will be based upon the necessary depthwithin the casing at which the cutting operation must be conducted inorder to permit complete removal of the Well head equipment.

With the cutting tool positioned in this preselected position, and withthe cutting members pivotally carried thereby being of a preselectedlength which is correlated to the diameter of the innermost of thecasing strings, the cutting members are pivotally extended into contactwith the internal wall of the innermost casing string preparatory tocutting through this casing string. The length of the cutting members isselected to provide maximum leverage against the innermost casingstring, and thus to provide the most eicient cutting action through thistubular element. The cutting tool is then rotated within the innermostcasing string to cause the cutting members carried thereby to cutthrough the innermost casing string to form an axially extending openingwhich extends around the entire circumference of the casing string.

Upon completion of the cutting action lby the cutting member, thecutting tool is removed from the well casing, and at least one otherelongated cutting member have a preselected length which is greater thanthe length of the rst mentioned cutting members is pivotally secured tothe cutting tool. The tool is then again lowered to a preselected pointor location within the innermost casing string. The preselected point orlocation of the cutting tool at this time will, as a general rule, beabove the location which it occupied during the initial cuttingoperation, but in any event, the location of the pivotal axes of theseveral now and longer cutting members attached to the cutting tool willbe above the location of the pivotal axes of the shorter cutting membersused during the rst cutting operation to cut through and around theinnermost casing string. The cutting members are then pivotally extendedoutwardly from the body of the cutting tool into the axially extendingopening formed during the initial cutting operation with the preselectedlocation of the cutting tool having been chosen to permit the new,longer cutting members to be extended through the axially extendingopening in the innermost casing string. With the relatively longercutting members extended into cutting position, the cutting tool is thenrotated to cause the new cutting members to cut through at least one ofthe outer casing strings which surrounds the innermost casing string.

The described sequence of steps may be repeated several times with asubstitution of a new and longer cutting member on the cutting tool ifsuch repetition is required in order to completely cut through aplurality of telsecoped casing strings.

Though not an entirely critical or essential method of accomplishingsuch positioning, the preselection of the position which is to beoccupied by the cutting tool in the well casing, and the manner in whichthe tool is brought to this position preferably entail mounting thecutting tool on the lower end of a tubing string which can be extendedfrom the drilling platform or barge into the well casing, and whichcarries intermediate its length, an extensible slip joint, a supportingswivel assembly and an interconnecting sub which is located between theswivel assembly and the cutting tool. The swivel assembly s then restedupon a shoulder or abutment formed on the casing at some point, and actsas a point of suspension for that part of the tubing string whichextends below the swivel assembly. To adjust the position of the cuttingtool and the cutting members carried thereby with respect to the casingand the previous holes which have been cut therein by cutting members ofother lengths, the length of the connecting sub which is positioned inthe tubing string between the swivel assembly and the cutting tool isthen varied to raise or lower the cutting tool to the required location.

The described method permits the length of the cutting members and theirposition within the multiple casing structure to be selected to yieldmaximum eiciency and optimum cutting performance. Though, of course,some time is involved in pulling the tubing string upon which thecutting tool is mounted for the purpose of exchangnig the variablelength cutting members, and exchanging the connnecting subs connected inthe string so as adjust the position of the cutting tool relative to thecasing, the time involved in such pulling and changing operations ismore than oifset and compensated by the eiciency obtained in the cuttingoperation, and the certainty with which the crew operating the cuttingtool can be apprised of its effectiveness and time of cutting the pluralcasing strings.

The apparatus of the invention, as will appear from the foregoingdiscussion, includes an elongated tubing string; a rotary tool securedto one end of the tubing string, and having a plurality of elongatedcutting members each detachably secured on said cutting tool forpivotation about a horizontal axis; piston means movably mountedrelative to, and cooperating with, the elongated cutting members forpivoting the cutting 4members into a cutting position; additionalelongated cutting members longer than the first mentioned cuttingmembers adapted for detachable pivotal securement to the rotary cuttingtool in place of the iirst mentioned cutting members; a swivel assemblyrotatably mounted on and surrounding the tubing string intermediate itslength; and a plurality of varying length connecting subsinterchangeably connectable in said tubing string between said swivelassembly and said cutting tool for selectively adjusting the distancebetween the cutting tool and the swivel assembly.

From the foregoing description of the invention, it will have becomeapparent that it is an important object of the present invention toprovide an improved apparatus for severing or cutting well casinglocated in a submarine environment.

An additional object of the present invention is to provide an apparatuswhich may be employed to more rapidly and eiciently cut through aplurality of concentrically or eccentrically disposed casing stringsunder circumstances where the cutting tool employed is suspended from aplatform or supporting structure which varies randomly in its distanceof separation from the cutting tool.

A further object of the invention is to provide an apparatus for cuttingthrough, or severing, several telescoping tubing strings at a commonlocation and from the inside outwardly with minimum wear occurring tothe cutting elements used to accomplish such severance of the telescopedtubing strings.

In addition to the foregoing described objects and advantages, othermeritorious features and beneficial results which can be obtained usingthe present invention will become apparent as the following detaileddescription of the invention is read in conjunction with theaccompanying drawings which illustrate a typical embodiment of theinvention.

In the drawings:

FIG. l is a schematic illustration, partly in elevation and partly insection, of a typical off-shore well installation, and illustrating acutting tool used in performing the method ot' the present invention andsuspended in a multiple casing well bore from a oating drilling barge.

FIG. 2 is an enlarged detailed view, partially in sec tion and partiallyin elevation, depicting a typical cutting tool which can be used inpracticing the method of the present invention, and illustrating thistool and its relation to the concentric casing strings employed forcasing an off-shore oil well as the tool appears immediately prior tothe commencement of a casing cutting operation.

FIG. 3 is a view similar to FIG. 2, but illustrating the use of thecutting tool in performing the first step of the casing cutting methodof the present invention.

FIG. 4 is a view similar to FIGS. 2 and 3, but illustrating the cuttingtool after it has been modified by the attachment of longer cuttingVmembers thereto and showing the tool as it is used in carrying out asubsequent step of the casing cutting operation.

FIG. 5 is a view of the cutting tool and telescoped casings similar toFIGS. 2-4, but illustrating the tool as further modified by the additionof yet longer cutting members, and showing the tool as it is beingemployed in the final step of the cutting operation.

Referring now to the drawings in detail and, initially to lFIG l, adrilling barge or platform is illustrated as oating on the surface of abody of water 12. A drilling rig 14 is mounted on the deck of thedrilling barge 10 and supports a downwardly extending drilling string16. The drilling string 16 includes along its length an extensible slipjoint or telescoping connection 18 which permits the overall length ofthe drilling string to vary as the drilling barge 10 may be `caused torise or fall with respect to the bottom of the body of water by waveactions, swells, etc.

The drilling string 16 extends downwardly into an inner casing 20 whichis coaxially positioned inside an intermediate or central causing 22 andan exterior or outer casing 24, this telescoping casing constructionbeing typical of that currently widely used for marine petroleumproduction. The exterior casing 24 is positioned in a bore hole 26 whichextends into the bottom 28 beneath the body of water 12.

A marine swivel assembly 30 is connected in the drilling string 16, andis dimensioned to bear against and rest upon an upwardly facing shoulder32 formed in the inner casing 20, preferably adjacent the upper endthereof. The function and mode of use of the marine swivel assembly 30is explained in detail in my copending application for United StatesLetters Patent, Ser. No. 374,- 719, filed June 12, 1964. It will sufficefor purposes of explanation of the present invention to point out thatthe swivel assembly 30 functions to provide a fixed point of suspensionsupport within the well casing for that portion of the drilling string16 which extends downwardly from the swivel assembly. Thus, the swivelassembly 30 in conjunction with the extensible slip joint 18 permit arelatively fixed location to be assumed by the cutting tool carried onthe lower end of the drilling string 16 hereinafter described.

Secured to the lower end of the drilling string 16, and positioned inthe FIG. l illustration below the well head at the top of the casing, isa cutting tool designated generally by reference character 34. Thecutting tool 34 is illustrated as secured to the drilling string 16through a connecting sub 36 of the box and pin type (see FIG. 2) Itshould be pointed out, however, that the location of the connecting sub36 in this specific position relative to the drilling string 16 andcutting tool 34 is not critical or required for the performance of themethod of the present invention, it only being necessary that theconnecting sub be positioned in the drilling string at some pointbetween the swivel lassembly 30 and the cutting tool 34. The role playedby the connecting sub 36 in the practice of the method of the inventionwill be hereinafter described in greater detail.

In FIG. 2 of the drawings, some of the structural details of the cuttingtool 34 are illustrated, and the tool is shown in the position which itshould occupy at the commencement of the casing cutting operation.Although a variety of types of cutting tools can be employed inpracticing the present invention, the type illustrated for explanatorypurposes is one in which a tubular body 38 surrounds a slidingly mountedpiston 40 which can be caused to reciprocate in the tubular body byfiuid directed through the drilling string 16 from the drilling bargeI10. The piston 40 carries at its lower end a downwardly facing knifeactuating member 42. The knife actuating member 42 is connected througha relatively small diameter rod 44 to a knife movement limiting member46. A helical compression spring 48 is provided in the lower portion ofthe bore in the tubular body 38 and bears against the knife movementlimiting member 46 for the purpose of `resiliently biasing the piston 40to its inoperative position as depicted in FIGURE 2 when the fluidpressure directed against the piston via the drilling string 16 isrelieved.

The cutting tool 34 has a plurality of axially extending slots 50 formedin the sides thereof for the accommodation of an equal number of cuttingmembers or knives 52 which are pivotally secured to the tubular body 38of the cutting tool by means of pivot pins 54. The cutting members orknives 52 each carry at their end most closely adjacent the pivot pins54, an arcuately shaped or tapered ear 56 which extends into the slot oropen space formed between the knife actuating member 42 and the knifemovement limiting member 46. The ears 56 are thus positioned to beengaged by the knife actuating member 42 at such time as the piston 40is moved downwardly within the tubular body 38 by the impress of fluidpressure directed through the drilling string 16. This construction Iandmode of operation of cutting tools of the general type described arewell understood in the drilling technology at the present time, andconstitute no part of the present invention except as tools of suchgeneral character are utilized in the practice of the method of theinvention, and in the overall apparatus employed therefor as hereinafterdescribed in greater det-ail.

A preferred method of practicing the present invention can best berelated -by referring conjunctively to the several figures of thedrawings in explaining the sequence -of perfomance of the several stepsutilized. The occasion for using the method of the invention forsevering or cutting the concentric casing strings arises at such time asa cased well has reached the end of its period of usefulness. At thistime, it is economically desirable to recover the expensive well headequipment (not illustrated) which is positioned at the top of thecasing, Iand it is also frequently necessary to remove the projectingportion of the casing and the well head equipment from the bottom of theocean or sea in order to comply with certain legal requirements whichapply to offshore drilling and production activities. In general, thecasing cutting operation will be carried out ra relatively shortdistance below the well head, it only being necessary to be certain thatthe concentric casing strings are severed or cut at a locationsufficiently low in the casing to permit these strings to beconcurrently pulled from the bottom together with the well headequipment secured to the upper end thereof.

Knowing the depth within the casing where the cuting operation is to becarried out, the length of the drilling string 16 between the swivelassembly 30 and the cutting tool 34 is selected to effectively locatethe cutting tool at the desired position in the casing when the swivelassembly 30 rests upon the casing shoulder 32 in the manner illustratedin FIG. l. Concurrently with the makeup of the drilling string 16 tomeet the requirements of positioning the cutting tool 34 at the desiredlocation, a Irelatively long connecting sub 36 is included in the tubingstring 16 between the swivel assembly 30 and the cutting tool 34. Thenthe drilling string 16 with the cutting tool 34 attached thereto is runinto the inner casing 20 until the swivel assembly 30 supports the lowerportion of the drilling string and the cutting tool 34 within the casingin the manner illustrated in FIG. l.

A suitable hydraulic iluid is next directed down through the drillingstring 16 against the piston 40 so as to move the piston downwardly inthe tubular body 38 and thus extend the cutting members 52 against theinternal wall of the inner casing string 20. The angle made by thelongitudinal axis of each of the cutting members 52 with thesubstantially vertical axis of the drilling string and of the tubular-body 40 of the cutting tool 34 will be a relatively acute or slightangle at the time of initial contact of the cutting members with theinner `casing string 20. With the cutting members l52 continuouslybiased a-gainst the inner casing 20 by fluid pressure, the drillingstring 16 is then rotated by a suitable rotary table or other equipmentcarried on the drilling barge 10, and such rotation of the drillingstring causes the cutting tool 34 to be rotated within the inner casing20. This rotational movement of the cutting tool 34 causes the cuttingmembers 52 to bite into the inner casing 20, and cut through the casinguntil the cutting members have assumed a radially outwardly extendingposition such as that depicted in FIG. 3.

When the cutting members 52 have reached the outwardly extendingposition shown in FIG. 3, an axially extending slot or opening 53 hasbeen cut into the inner casing 20, and such slot extends completelyaround this inner casing or, stated differently, the casing has beensevered or cut into an upper and a lower portion. It is important tonote at this point in the discussion of the present invention that thelength of the cutting members 52 is initially selected with a knowledgeof the internal diameter of the inner casing 20 so that sufficientleverage can be obtained on the cutting members to assure that they willcut easily and quickly through the inner casing. The limitations ofdiametric space within the inner casing 20 are such that the optimumlength for the cutting members 52 utilized in the described initialcutting step can frequently not be suiciently great that such cuttingmembers can extend to, or contact, the intermediate or central casingstring 22. This is the situation which is illustrated in FIG. 3. Onother occasions, however, it may be possible that some cutting of thecentral or intermediate casing string 22 can be accomplished with theinitially used cutting members 52.

The cutting tool 34 may be, and preferably is, constructed with uidbypasses (not shown) which become open to the iiuid `driving the piston40 at such time as the piston reaches its lowermost position and thecutter members 52 are fully outwardly extended as depicted in FIG. 3.The occurrence of some bypass or bleeding olf of the power uid at thistime will permit a positive indication to be obtained on the drillingbarge of the fact that the cutting members 52 have accomplished andcompleted their cutting operation, and that at least the inner casingstring has been cut through. A further indication of the Lachievement ofthis status also results from a reduction in the torque which must be-applied to the drilling string 16 in order to drive it in rotarymotion.

Upon completion of the step of the process by which the inner 4casingstring 20 is cut through in the manner described, the drill string 16 isremoved from the well casing and that portion of the string between theswivel assembly and the cutting tool 34 broken down and again made up,this time to include a relatively shorter connecting sub 60 than theconnecting sub 36 which was utilized initially for the cutting operationby which the inner casing string 20 was severed. The cutting members 52utilized on the cutting tool 34 are also replaced so that relativelylonger cutting members or knives 62 are pivotally mounted on the tubularbody in place of the shorter cutting members 52 which were originallyemployed (See FIG. 4). The length of the cutting members 62 which areused in the second cutting operation is selected so that these cuttingmembers are substantially longer than the cutting rmembers initiallyused, and also so that, in most instances, though not necessarily all,the cutting members 62 will extend to, and be able to sever, theintermediate or central casing string 22 during the subsequent cuttingoperation to be described. The size of the connecting sub 60 is selectedto correlate with the length of the cutting members 62 which are used sothat the free ends of the cutting members 62 will be able to passthrough the axially extending slots or openings 53 formed in the innercasing string 20, and will either initially be in a position in theannulus between the inner and intermediate casing strings 20 and 22, orwill bear against the internal surface of the intermediate casingstring. Viewed in another way, the sub 60 is selected so that withoutalteration of any other part of the portion of the drill string 16 whichis positioned `between the swivel assembly 30 and the cutting tool 34,the length of this portion of the string is shortened so as to bring thecutting tool to a relatively higher position in which the longer cuttingmembers 62 can move into and through the relatively small slot oropening formed through the inner casing string 20 by the initial cuttingoperation using the relatively shorter cutting members 52.

With the lower portion of the drilling string 16 made up in thedescribed fashion, the drilling string is again lowered into the innercasing string 20 until the swivel 30 comes to rest upon the supportingshoulder 32 of the well casing. The hydraulic fluid is then againdirected through the hollow interior of the drilling string 16 againstthe piston 40 and forces the piston downwardly against the ears 56 ofthe cutting members `62. Thus, the cutting members 62 are biasedradially outwardly so that their upper edge bears against, or is incontact with the downwardly facing upper edge of the slot 53, which wascut through the inner casing string 20 during the initial cuttingoperation. The drilling string 16 is then rotated, and the rotativemotion of the cutting tool 34 secured thereto coupled with the constantoutward bias of the cutting members 62 results in the slot or opening 53being enlarged in an axially upward direction, and also results in thetips of the cutting members 62 being extended further in a radialdirection with respect to the cutting tool 34 and with respect to theinner casing string 20.

Where the cutting members 62 are of sufficient length to extend intocontact with the intermediate or central casing string 22, the cuttingaction of these members will continue on the inner surface of theintermediate casing string until this casing string has been cutthrough, and the cutting members 62 attain the horizontal statusdepicted in full lines in FIG. 4 of the drawings. Thus, both the innerand intermediate casing strings 20 and 22 have then been cut completelythrough, and there remains only the outer casing string 24 which has notbeen severed. It should be pointed out here, however, that in some typesof casing installations, the intermediate casing string 22 may besuiliciently larger than the inner casing string 20 that the cuttingmembers 62 which are necessarily used in the second step of the cuttingprocedure will not reach to, or engage, the intermediate casing string22. In such eventuality, the steps of the method as hereinafterdescribed are nevertheless followed, and eventually cutting members ofsufiicient size to extend through and sever all of the telescoped casingstrings will be utilized, and all of the casing strings will be cleanlyand eiciently cut at the desired location.

The attainment by the cutting members 62 of the fully extended,substantially horizontal position shown in FIG. 4 will be known at thesurface from the torque reduction and the hydraulic power fluid pressurereduction herein- Abefore described. At this time, the uid pressure onthe piston 4i) is released to permit the spring 48 to bias the cuttingmembers 62 to their retracted positions, and the drilling string 16 isagain withdrawn from the well casing to permit a relatively shorterconnecting sub 66 to be connected in the string in place of theconnecting sub 60. Also after the removal of the drilling string 16 fromthe well, new cutting members 68 of yet greater length are pivotallysecured on the tubular body 38 of thecutting tool 34 with the cuttingmembers 68 being selected to permit them to extend through the openingin the inner and intermediate casing strings 20 and 22, and into contactwith the outer casing string 24. The length of the connecting sub 66 isselected so that the lower free ends of the cutting members 68 will beadjacent, or slightly above, the lower edge of the slot or opening 53formed in the internal casing string 20 when the swivel assembly 30occupies its position of support at the top of the well casing.

With the drill string 16 made up in this way, the string is againlowered into the casing until the swivel 30 comes to rest on thesupporting shoulder 32. When the drilling string 16 is thus positioned,the cutting tool 34 will occupy the position illustrated in FIG. 5, andthe cutting members 68 carried thereby will be in their retractedpositions as shown in dashed lines in FIG. 5. The hydraulic uid is thendirected through the hollow interior of the tubular drilling string 16to bias the piston 40 forcibly downwardly and cause the relatively longcutting members 68 to be pivoted outwardly through the openingspreviously cut in the internal and intermediate casing strings 20 and22, and to bear against either the internal surface of the outer casingstring 24, or against the upper edges of the openings cut through theinner and intermediate casing strings 20 and 22. In either event, withthe continued downward bias of the piston 40 by hydraulic pressure, therotation of the drilling string 16 is commenced, and the cutting members68 commence to either enlarge the slots or openings formed through theinner and intermediate casing strings 20 and 22, or to cut through theouter casing string 24, or both of these reaming and cutting operationsmay occur simultaneously.

After a brief period of rotation of the drill string 16 with continueddownward bias of the piston 40, the cutting members 68 are ultimatelycompletely extended so that they occupy the horizontal status depictedin FIG. 5. At this time, all of the telescoped casing strings 20, 22,and 24 have been completely cut through by the cutting operationshereinbefore described. The completion of the cutting of the outercasing string 24 is reflected on the drilling barge by a reduction inthe torque required to rotate the drilling string 16, and by a reductionin the pressure being applied to the hydraulic uid which biases thepiston 40 downwardly. At this time, the hydraulic pressure on the piston40 can be released to permit the spring 48 to bias the piston upwardlyand the cutting members 68 to be retracted. The tubing string and thecutting tool 34 carried thereby can then be retrieved from the wellcasing, and appropriate tools can be connected to the well head orequipment attached thereto to lift the upper portion of the severedcasing and the well head equipment to the surface so that it can beloaded onto the drilling barge 10 and thus completely salvaged.

From the foregoing description of the invention, it will have becomeapparent that this invention provides a highly effective apparatus forquickly cutting through a plurality of concentrically or eccentricallydisposed strings of Well casing so that the portion of the casingstrings adjacent the well head can be removed from the earth, and all ofthe equipment which is secured to the well head can be recovered. Themethod can be easily practiced, involves a minimum of wear and breakageof apparatus used in practicing the method, and affords positive andeasily recognized indications to operating personnel of the times atwhich the several cutting steps involved in the method have beencompleted.

Although a specific embodiment of the apparatus of the invention hasbeen hereinbefore defined in order to provide typical examples of themanner in which the invention is to be practiced, it rwill be understoodthat various changes and modifications can be made in the variousstructural elements of the apparatus used without departing from thebasic principles of the invention. All changes and modifications of thistype are therefore deemed to be circumscribed by the spirit and scope ofthe invention except as the same may be necessarily limited by theappended claims, or reasonable equivalents thereof.

What is claimed is:

1 Apparatus for severing a plurality of telescoped well casmgscomprising:

(a) an elongated tubing string diametrically dimensioned to facilitateinsertion of a major portion of said tubing string in the innermost oneof said telescoped well casings;

(b) a rotary cutting tool secured to one end of Said elongated tubingstring on said major portion of the tubing string and dimensioned forinsertion in the innermost casing, said cutting tool having (l) aplurality of elongated cutting members each detachably secured on saidcutting tool for pivotation about a horizontal axis, and of a length tocontact the internal wall of said innermost casing and shorter thanrequired to contact the internal wall of the outermost casing of saidtelescoped well casings, and

(2) piston means movably mounted relative to, and cooperating with7 saidelongated cutting members for pivoting said cutting members into acutting position in contact with the internal wall of said innermostcasing when said piston means is moved under the impress of a hydraulicfluid directed through the tubing string;

(c) additional elongated cutting -members longer than said rst-mentionedcutting members adapted for detachable, pivotal securement to saidrotary cutting tool in place of said lirst-mentioned cutting members;

(d) a swivel assembly rotatably mounted on, and surrounding, said tubingstring intermediate its length, said swivel assembly being diametricallydimensioned to contact and engage one of said casings when the portionof said tubing string carrying said cutting tool is lowered into saidinnermost casing; and

(e) a plurality of varying length connecting subs interchangeablyconnectable in said tubing string between said swivel assembly and saidcutting tool for selectively adjusting the distance between said cuttingtool and said swivel assembly.

2. Apparatus as defined in claim 1 and further characterized to includean extensible slip joint connected in said tubing string on the oppositeside of said swivel `assembly from said cutting tool.

3. Apparatus for severing a plurality of concentrically disposed wellcasings from the inside of such casings outwardly comprising:

(a) an elongated tubing string adapted for insertion of a portionthereof in the innermost one of said concentric well casings;

(b) a rotary cutting tool secured to one end of said elongated tubingstring for insertion in the innermost casing of said concentric casings,said cutting tool comprising:

(l) a tubular body having elongated axially extending slots formed inthe sides thereof;

(2) an elongated cutting member detachably mounted in each of said slotsand having a portion projecting into the interior of said tubular body,each of said slots being at least twice the length of said elongatedcutting member to facilitate accommodation of detachably mounted cuttingmembers of lengths substantially longer than said first mentionedcutting members; and

(3) piston means movably mounted in said tubu- 11 lar body relative tosaid elongated cutting niembers and cooperating with said cuttingmembers for pivoting said cutting members into a cutting position forcutting the internal wall of the innermost casing of said concentriccasings when said piston means is moved downwardly in said tubular body;

(c) a swivel assembly rotatably mounted on, and surrounding, said tubingstring intermediate its length for permitting said tubing string torotate within said swivel assembly when said swivel assembly is heldstationary;

(d) a connecting sub quick detachably connected in said tubing stringbetween said swivel assembly and said tubular body for quick detachmentand replacement by connecting subs of various lengths; and

(e) an extensible slip joint connected in said tubing string on theopposite side of said swivel assembly from said cutting tool.

12' References Cited UNITED STATES PATENTS DTHER REFERENCES CompositeCatalog of Oil Field Equipment and Services, 1962-63, Houston, Tex.,Gulf Pub. Co., vol. 3, p. 4634.

CHARLES E. OCONNELL, Primary Examiner l. A. CALVERT, Assistant ExaminerUS. Cl. X.R. 166-78

